The effects of pyridine derivative additives on interface processes at nanocrystalline TiO ₂ thin film in dye‐sensitized solar cells

Abstract

Abstract 2‐Methyl‐4‐propoxypyridine, a new pyridine derivative, has been synthesized and used as an additive in the liquid electrolyte of dye‐sensitized solar cells (DSSCs). Compared with 2‐methylpyridne and 4‐ tert ‐pyridine, they were employed to study the influence of the pyridine derivative additives on the rate of recombination at the electrode/dye/electrolyte interfaces and band edge shift of TiO 2 , which were measured by time‐resolved mid‐infrared absorption spectroscopy and Mott–Schottky analysis, respectively. It was found that the rate of interfacial charge recombination was enhanced when the pyridine derivative additives were present in the electrolyte. Meanwhile, the additives caused a negative shift of the band edge. However, the net effect of pyridine derivative addition was to improve the open‐circuit photovoltage according to the photoelectrochemical measurement, indicating that negative shift of conduction band of TiO 2 was a predominant factor in improving the open‐circuit photovoltage. Also, the result was strongly supported by the dark current measurement. Therefore, it provides a microscopic account for the function of the pyridine derivative additives on the open‐circuit photovoltage enhancement of the DSSCs. Furthermore, the decrease of the short‐circuit photocurrent of the cells was also attributed to the slower dye regeneration due to the addition of additives from the results of cyclic voltammetry measurement. Copyright © 2007 John Wiley & Sons, Ltd.